Enterotoxigenic B. fragilis (ETBF), but not nontoxigenic B. fragilis, is known to induce tumour formation in the ApcMin/+ mouse model [26–28], indicating that any association between this species and CRC development may be specifically related to the presence of B. fragilis toxin (BFT). The gene discussed is PITX1; the disease is colorectal carcinoma.